Audiology Masking Calculator – Initial Masking Level: Our Audiology Masking Calculator automates the math so you can focus on patient care. It calculates initial masking levels (IML) and maximum safe levels (MML) for both AC and BC based on the threshold values you enter. No more scribbling formulas on scraps of paper or second‑guessing your safety margins.
Audiological Masking Calculator
Calculate Initial Masking Level (IML) and Maximum Masking Level (MML) for AC and BC
Threshold Values Input
Important: BC thresholds should not be higher (greater) than AC thresholds at the same frequency. The calculator will highlight invalid entries in red.
Right Ear Thresholds
| Frequency (Hz) | AC (dB HL) | BC (dB HL) |
|---|---|---|
| 250 | ||
| 500 | ||
| 1000 | ||
| 2000 | ||
| 4000 |
Left Ear Thresholds
| Frequency (Hz) | AC (dB HL) | BC (dB HL) |
|---|---|---|
| 250 | ||
| 500 | ||
| 1000 | ||
| 2000 | ||
| 4000 |
Air Conduction (AC) Masking Results
| Frequency (Hz) | Need Masking? | IML (dB HL) | MML (dB HL) |
|---|
Bone Conduction (BC) Masking Results
| Frequency (Hz) | Need Masking? | IML (dB HL) | MML (dB HL) |
|---|
Masking Formulas & Instructions
When to Mask for AC
Mask when:
[AC(TE) − BC(NTE)] ≥ 40 dB
Where:
- AC(TE) = Air Conduction threshold of Test Ear
- BC(NTE) = Bone Conduction threshold of Non-Test Ear
AC Initial Masking Level (IML)
IML = AC(NTE) + 5dB + 10dB
Where:
- AC(NTE) = Air Conduction threshold of Non-Test Ear
- 5dB = MEM correction
- 10dB = Safety factor
AC Maximum Masking Level (MML)
MML = BC(TE) + IA
Where:
- BC(TE) = Bone Conduction threshold of Test Ear
- IA = Interaural Attenuation (40dB for headphones, 70dB for inserts)
When to Mask for BC
Mask when:
ABG > 10 dB
Where:
- ABG = Air-Bone Gap in Test Ear (AC(TE) – BC(TE))
BC Initial Masking Level (IML)
IML = AC(NTE) + 5dB + 10dB + OE
Where:
- AC(NTE) = Air Conduction threshold of Non-Test Ear
- 5dB = MEM correction
- 10dB = Safety factor
- OE = Occlusion Effect (20dB at 250Hz, 15dB at 500Hz, 5dB at 1000Hz)
BC Maximum Masking Level (MML)
MML = BC(TE) + IA
Where:
- BC(TE) = Bone Conduction threshold of Test Ear
- IA = Interaural Attenuation (40dB for headphones, 70dB for inserts)
Instructions for Use
- Enter threshold values for both ears (AC and BC)
- Important: BC thresholds must not be higher (greater) than AC thresholds at the same frequency. This is an audiological principle – bone conduction thresholds cannot be worse than air conduction thresholds.
- Select the Test Ear (the ear being tested)
- Select the Transducer Type (headphones or insert earphones)
- Click “Calculate Masking” to determine masking requirements
- Review the results tables for both AC and BC masking needs
- Apply the calculated IML (Initial Masking Level) to start masking
- Never exceed the MML (Maximum Masking Level) during testing
Step-by-Step Guide to use Audiology Masking Calculator
Our free Audiology Masking Calculator is designed to mirror typical clinical forms. Here’s what you’ll fill in:
- Enter AC and BC thresholds (dB HL) for both ears at standard frequencies (250, 500, 1000, 2000, 4000 Hz).
- Remember: BC thresholds must never exceed AC thresholds at the same frequency—bone can’t be worse than air! The calculator flags any violation in red.
- Select which ear you’re testing (Right or Left).
- Choose your transducer: Supra‑aural Headphones (IA = 40 dB) or Insert Earphones (IA = 70 dB).
- Click “Calculate Masking.”
- Review two tables: one for AC masking, one for BC masking. Each shows IML and MML.
- Apply IML noise to the non‑test ear and begin threshold measurement. Never exceed MML—safety first.
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